Dimerization of unsaturated hydrocarbons



United States PatentOfiice DHVIERIZATION OF UNSATURATED HYDROCARBONS Karl Ziegler and Hans Georg Gellert, Mulheim an der Ruhr, Germany No Drawing. Application June 19, 1951, Serial No. 232,475

Claims priority, application Germany June 21, 1950 14 Claims. (Cl. 260-68345) This invention relates to the 'dimerization of olefins. One ob ect of this invention is a method for dimerizing organic hydrocarbons having more than two carbon atoms in their molecule. This and still further objects will become apparent from the following description:

According to the invention, unsaturated organic hydrocarbons containing more than two carbon atoms in their molecules, or mixtures of these unsaturated hydrocarbons, are dimerized by heating such hydrocarbons to a temperature of about 80 to 250 C. in the presence of hydrides or certain organo compounds of alumintun or ts next highest group members in the periodic system, 1. e. gallium and indium or its adjacent group member beryllium, which act as exceptionally elfective agents for forming dimers of these-hydrocarbons.

These new dimerization activators have the general formula Me(R)n, in which Me' is one of the aforementioned metals, i. e. aluminum, gallium, indium and beryl- 'lium, n is the valence of the metal, and R is at least one of hydrogen, monovalent, saturated aliphatic radicals, monovalent aromatic organic radicals or any compounds thereof. Suitable activators according to the invention are, for example: Be(C2Hs')2, AlHa, HAl(CHs)-z, H2AIC2H5, Al(CH3)3, A1(C2H5)3, Al(CsH5)3, Ga(CH3)3, In(CH3)s, Be(CsH5)2," Al(CsH13),3, Al(C1aH3'1)3, Ga(CsH5)3, In(CsH5)z, and the like.

These new dimerization activators may also be present in the form of their known, and in many cases very stable organic molecular compounds with, for instance, ethers, thioethers or amines, or else in complex linkage with alkaline metal hydrides, alkylsor aryls." "Examples of these activator compounds are: NaBe(C2H5)3, LiAlH4, LiAl(C2H5)4, NaAl(CsH5)4 and the like.

The dimerization, according to the invention, is carried tion may be carried out at normal pressures or increased pressures up to the highest possible pressures, as, for example, pressures of 2,000 atmospheres or still higher as may be practically obtained in present operations. The

activators in accordance with the invention may not be 1.

true catalysts in the scientifically strict meaning of the word, as they do not remain during the reaction exactly the same as they were when originally added. They may out at a temperature of about 80 to 250 C. The reacbe present in small non-stoichiometrical quantitiesand still bring about comparatively large conversions. The

activators form compounds with the olefins and such f compounds are frequently contained as by-products in the reaction tion is used herein and in the claims, there is meant thereby the formation of a dimer of two unlike unsaturated hydrocarbon molecules, as well as the formation products. When the expression dimerizaof a dimer of two like molecules of unsaturated hydrocarbon. A Any unsaturated hydrocarbons which have more than two carbon atoms in the molecule may be used to form the dimers in accordance with the invention. A single unsaturated hydrocarbon may form a dimer with itself, or two different unsaturated hydrocarbons may be dimerized. Olefins which have a terminal double bond, and olefins having a double bond in the intermediate position may beusedjn accordance with the invention.

The higher olefinsmay be used in accordance with the invention, and it has been found that alpha olefins react more rapidly than olefins which have the double bond in the intermediate position. There is, however, no fundamental difference with regard to the reaction products obtained. Thus, for example, andlheptene-(3) the dimeric heptenes produced are idenica This is due to the fact that the double bond is able to migrate under the influence of the organo metal activators. From heptene-( 3), be produced at times in accordance with the invention and this heptene-(l) will form the dimer.

In addition to the dimers, polymers may also be formed. The formation of a dimer, however, is strongly preferred. Thickly viscous polymeric reaction products may be obtained in addition to the dimers in a ratio of 1:1 in certain cases, as for example with the use of heptene-( 3), if heating is efiected for comparatively long periods of time.

The method, according to the invention, is by no means limited to olefins of relatively low molecular weight. It is possible to, for example, convert dodecene in accordance with the invention.

Example 1 Al(C2H5)s was diluted with 10 times its volume of pentane. To this was added times the molar quantity of propylene. The mixture was made in an autoclave'and heated at a temperature of 180 C at a pressure of 170 atmospheres. The pressure was noted to drop to 40 atmospheres within a few hours. Additional propylene was added under pressure, and the reaction started again. The reaction was continued in this manner until I the autoclave was completely filled with the reaction products. These reaction products contained a small initial amount of hydrocarbons of the C4 and C5 series. About 70% of the propylene was dimerized into l-methyl-lpropyl-ethylene 'C=OH2 CHzCHz CH2 and which boiled at C. and had an n =1.3920. products, a few parts per In addition to these reaction g 100 of trimeric propylene and higher polymers were also obtained;

Example 2 used. l-2% of aluminum trimethyl Al(CH3)3 by weight of the propylene is added to the propylene in an autoclave,

' While the propylene is under pressure, but still in gaseous phase. The temperature is then raised to 200 C., whereupon the pressure increases to about 170 atmospheres.

After several hours the pressure decreases to about 30-40 M atmospheres, whereupon new propylene may be again pressed into the autoclave, thereby repeatmgthe reaction until the autoclave is substantially filled with the propylene conversion product.v Pressure is then released and the autoclave is opened. Colorless, readily movable l1qu1d is obtained, which, upon distillation, shows at least of the used propylene in the form of a llqllld having'a constant boiling point of 65 C. and essentially representing l-methyl-l-propyl-ethylene [Z-methyl-pentene-(1)] CHE? C=CH2 CHaCHaC:

Analysis shows that the hydrocarbon is very pure and Patented Nov. 23, 1954 in the case of heptene-(l) for example, heptene-(l) may trimer propylene as well as still higher boiling constitu cuts of oily consistency.

Example 4 Example 1 was repeated using the same conditions and materials as they are set forth,- except that respectively Al(C2l-I5)s, Al(CsH1)3 and Al(CeHs)s were substituted for the aluminum trimethyl there prescribed. Essentially the same reaction products were obtained as set forth in the preceding example.

The dimerization velocity of the propylene increases rapidly with the amount of the initial added metalo-organic compound. Thus, when using about l20% of aluminum trialkyl in the propylene, the reaction velocity is so high that the same may be advantageously utilized for effecting continuous operations. in this manner the solution of the activator in propylene under pressure is permitted to pass from the top into a heated reaction chamber or alternatively into a tubular coil heated to about 200240 C. at the lower end of which there is recovered a solution of the rnetalo-organic activator and dimer propylene together with unused propylene. Components may be easily separated by distillation. Propylene and recovered activator material are recycled into the process. The activator remains effective for a long period of time and despite the relatively large addition of 20% activator material initially used, the account of such activator material continuously required for the replenishment of activator material loss is relatively small in relation to the yields of variated propylene dimer.

All a-olefines of the formula CnH2n+LCH=CH2 react similarly to propylene. They can all be converted under the same conditions into dimer products of the general formula There are always, however, obtained by way 1 of byproducts certain amounts of isomersof the initially used olefins with differently positioned double linkages; Proceeding from butene-(l) preponderantly dimer butene.

C= CH2 cz Hs of a B. P. of 118 is obtained, but also butene-(Z). Proceeding from pentene-(l) preponderantly dimer pentene of a B. P. of 164 is obtained, but in addition pentene- (2). Proceeding from hexene-(l) preponderantly dimer hexene C=CH2 C4412 of a B. P. of 88-89" (14 mm.) is obtained, but also a mixture of hexene-(Z) and hexene-(El). Starting with dodecene-(l) large amounts of dimer dodecene C=CH1 mHzr When proceeding occurring as a side reaction to the dimerization of, for IHSlIHIICQ hCXCHB as shownin formula the reverse is possible for olefins with intermediate double linkage. Within the-conditions of operation the following equilibrium is obtained:

This has the effect thatnotonly a-olefins, but also isomer compounds with other than tat-positioned double linkages are finally convertedto a very large extent when heated in the presence of the aforementioned dimerization activators to form' the dimers of the corresponding e-olefins. This, however, will require a longer period of time than is necessary when subjecting pure-:a-olefins. to the dimerization reaction. The dimerization of :the pure pentene-(Z) into thedeceneof the formula formed in a side reactiom This will finally also become dimerized thoughgrequiring-a much longer period of These differentialreaction'velocities-may,-on the other hand, also beutilized to remove by-dimerization I reaction'u-olefins from a mixture of a-olefins with the time.

less reactive olefins of intermediate double linkages.

The velocity of the-dimerizationof pure a-olefins is, independent of the size of the molecule, always approxi-- This is true even though mately of the same magnitudes decrease with increasing this velocity in normal cases molecular-weightr This .is so becauset-heconcentration of the unsaturated endzgroupingdecreases in the liquid olefinwith'increasing molecularweight; It has not-been possible to establish any limit to the-dimerization capacity. Even octadecene fl) may be readily converted into r a dimer which probably corresponds-to the formula CiaHar C=CH2 0511a The scope of application :of the new method to olefins with intermediate double linkage is, however, more limited. When in equilibrium;the proportion of ot-olefinin the mixtureconstantly decreases with increasing chain length of the olefins, because of the increasing number of possible'products. For this-reason the reaction velocity of these olefins decreases rapidly with increasing chain length and finally approaches alimit beyond which. dirnerization can no longer be accomplishedwithin any practically useful timeperiodsr' This'limitis approximately olefins with about 1'2 carbonatoms in the chain.-

The olefins useful with thepresent method straight chain type.

such as \CHCH=CH2 on,

and

CHa-Clfle-CHLCHmCH.(3115.0112-GHLCHz.CH3v

and aralkyl hydrocarbons such as for the dimerization in accordance need not be exclusively of the Also branched chain hydrocarbonsmay be dimerized in accordance with the invention. It is further possible to eifect mixed dimerization of two different olefins. When thus heating, for instance, under the conditions above described, a mixture of propylene and u-butylene with several percent of aluminum alkyl at a temperature of 200 C. or with aluminum hydrid for several hours at 7080 C. followed by heating to 200- 220 C., an excellent yield of a colorless liquid is obtained which, upon distillation, in an efiicient column produces approximately equal proportions of the following hydrocarbons and In a similar manner dimerization may be effected between propylene and hexene, pentene and heptene, butene with dodecene, etc., the number of such combinations being practically unlimited.

It is a disadvantage of the last-described method that the same always produces mixtures of products of ordinary dimerization with products of mixed dimerization. It is, however, possible to control these reactions, leading them along predetermined directions.- This may be accomplished, for instance, by the followlng artifice: aluminum trialkyl is used as the activator material, using as the alkyl component-one of the same C number as one of the two olefin components. Thus, for instance, aluminum tributyl is used whenit is intended to combine butene-(l) and propylene. The aluminum tributyl is then heated with 3 mols of propylene (under pressure) to a temperature'of 130-150 C.-, wherebythe propylene disappears, being taken up by thetributyl aluminum to form an intermediate compound.-- If the latter is then heated under pressure to the;- same-temperature with u-butylene disappearance or atleast substantial disappearance of the butylene occurring,-- the aluminum tributyl is reformed and predominantly l-butyll-methyl ethylene C Hn C=CH2 C x If, however, aluminum tripropyl is used and-the operation is so conducted that at firstbutene and then propylene are permitted to react and continuing to add these two olefins in that sequence preponderantly a polymer of the following formula is obtained.

ag C=GH2 CzHs In a similar manner the mixed dimerization of hexene with pentene or heptene with propene may be accomplished; Many other like combinations may be used with equal success. Depending upon the olefins used and the sequence of their addition certain predetermined products may be obtained. v

The method in accordance with the invention is not, however, limited to pure olefins or mixtures of two ole-, fins. The reaction. may be also efliected if therolefins or olefin mixtures are admixed with other materials substantially inert to the'rnetalo-orga'nic activators. Among such inert materialsare particularly. saturated or aromatic hydrocarbons. Thus, for instance, in lieu of the pure propylene used in the above example, any other C3 fraction, such as one consisting of propane and propylene may be used. After the dimerization of the propylene the propane may be easily separated by distillation.

It is also possible to use mixtures of more than two olefins as such, or in mixture, or solution with other hydrocarbons, or inert solvents. The practical eflFect'is then always such that mixtures of hydrocarbons are formed, having in the average a double molecular size. In this manner it is easily possible to convert, for instance, the C3 to C6 cut derived from petroleum cracking into a mixture of hydrocarbons with from 6 to 12 carbon atoms. Of these the lower boiling components may then be directly obtained as highly valuable motor fuels while the higher boiling constituents may serve as the starting products for such processes as, for'instance, oxosynthesis, thus opening "the door into the'impor'ta'nt and valuable territory of alcohols, aldehydes and acids with about 8 to-l3 carbon atoms.

Example 5 Dodecene was mixed with 4% Al(CzH3)s etherate and heated for 16 hours at 230 C. At the end of this time a dimer was recovered having a boiling point of 155 C. at 0.1 mm. The dimer formed was determined to have the following equation:

Example 7 100 kg. of liquid propylene were mixed in a pressure container with 10 kg. of aluminumtripropyl and were then pressed through a tubular coil heated to a temperature from 200 C. to 210 C. The tubular coil was provided at its lower end with a pressurerelease valve and the lower end of the tubular coil was cooled. The valve terminates in a container filled with nitrogen. The propylene AI(C3H7)3 mixture is pressed through thelheated tubular coil at such velocity that the period of its remaining within the heated zone is from one half to two hours. When proceeding in this manner, there is continuously obtained a mixture of from 70 to parts of Z-methylpentene-(1) with some unchanged propylene as. well, as smallportionsof higher polymer products the same con,- taining additionally the aluminum organo compounds by way of dissolution in the distilled over products.

The hydrocarbons may be separated by distillation and the distillation residue is again mixed with kg. of propylene and the operation is repeated as above set forth. it is possible to dimerize in this manner at least 1000 kg. of propylenein a substantially continuous man'- ner since the aluminum; organic,liquidicontact material retains its fi ctivenessiora longperiod oi time, 1 When the efiectiveness of the contact material becomes impaired, it is of advantage to distill the same invacuum or and preferably a fairly high vacuum to thereby. free the same from the difficultly volatilizable components. If necessary, the contact material may be replenished by the addition of fresh aluminumtripropyl.

Example 8 1 kg. of pentene-(l) and 50 grams of Al(C2H5)a are heated in an autoclave of about 3 liters contents under exclusion of air to a temperature of about 200 C. The pressure rises temporarily to about 33 atmospheres and thereupon decreases during a period of about 15 hours down to about 12 atmospheres. After cooling, the autoclave content being substantially liquid, is washed with diluted hydrochloric acid to free the same from aluminum, whereupon the same is dried and distilled. In this manner there is obtained in addition to some unchanged pentene a total of about 890 grams polymer product, of which about 700 grams have a constant boiling point of about 164 C. and which demonstrate upon closer analysis to besubstantially pure 2-propylheptene When repeating this example except that pentene-(Z) Example 9 440 grams of propylene and 720 grams of pentene- (l) both completely dry and free from air are admixed with 10 grams of solid aluminum hydride from which its ether content has been previously removed to the maximum possible extent (of about 30% ether) by careful keeping at a relatively high vacuum. The mixture is heated in an autoclave at first for a period of about 2 hours to a temperature of about 70 C. and is thereafter heated for hours at a temperature of about 210 C.

Thereafter the substantially liquid autoclave content is washed with diluted hydrochloric acid and is then carefully distilled.

There were obtained when proceeding in accordance with this example 40 grams of propylene, 90 grams of pentene, 150 grams of pure Z-methylpentene-(l) of boiling point 63 C., 400 grams of a hydrocarbon of the Ca series of a boiling point of about 118-1 19 C. and 200 grams of substantially pure 2-propylheptene-(l) of a boiling point of about 167 C. In addition, intermediate fractions were obtained which upon separation yielded further amounts of the above named products.

The hydrocarbon of the Ca series yields upon cleavage with ozone a mixture of ketones of the composition C7H14O which upon analysis proved to be a mixture of about equal parts of methylamylketone and dipropylketone of the respective formulae The C8 hydrocarbon may thus be expected to contain the .two components CH: CaHr C CH: G=CH2 C5Hn (33H? In all of the foregoing examples there may be used in lieu of the activators specifically therein referred to any other of the activators within the general group definitions herein set forth and especially those for particularly good results herein specifically set forth. The purest products are, however, always then obtained when proceeding with the dimerization of the olefins in accordance'with the invention utilizing for the activator alkyl radicals of the same carbon number as they are used in the olefin. Similarly the purest products are also then obtained when within a preferred embodiment of the invention aluminum hydride or beryllium hydride are used. .These are, however, only refinements and are not as such absolutely necessary. Thus, for instance, it is readily possible to substitute for the of Examples 1 and 8 .theequivalent amount of any of the following:

CH3 Al CRT-5H /GH: CHr-CH Cal- 1 a No material changes are otherwise necessary when using these substitute activators in the reaction or procedure referred to and the results obtained, as well as the reaction conditions are substantially the same as those described in the hereinabove referred to examples.

Though any of the other activator compounds herein referred to and usable within the scope of our invention give good results, the triethylaluminum Al(CzH5)3 is the preferred activator material because the same is the most readily available at this time and therefore lends itself best to practical use in commercial applications. It is, of course, obvious that many embodiments and dimerization of many different unsaturated hydrocarbons may be made in accordance with the invention. The invention is, therefore, in no way intended to be limited by the terms and the examples, being limited only by the appended claims or their equivalents.

We claim:

1. Method for dimerizing unsaturated straight-chain hydrocarbons containing more than two-carbon atoms in the molecule, which comprises heating such hydrocarbons at a temperature of about to 250 C. in the presence of a dimerization activator having the general formula M(R)n, in which Me is one metal selected from the group consisting of beryllium, aluminum, gallium and indium; R is at least one substituent selected from the group consisting of hydrogen, monovalent saturated aliphatic hydrocarbon radicals, and monovalent aromatic hydrocarbon radicals, and n is the valence of the metal Me, and recovering a dimer.

2. Method according to claim 1 in which said unsaturated hydrocarbons consist of a single unsaturated hydrocarbon.

3. Method according to claim 1 in which said unsaturated hydrocarbons are a mixture of at least two diflerent unsaturated hydrocarbons.

' 4. Method according to claim 1 in which said hydrocarbons are olefins having a terminal double bond.

5. Method according to claim 1 in which said hydrocarbons are olefins having an intermediate double bond and not in excess of 12 carbon atoms.

6. Method according to claim 1 in which said unsaturated hydrocarbons are branched chain unsaturated hydrocarbons.

7. Method according to claim 1 in which said unsaturated hydrocarbons contain admixed therewith aromatic hydrocarbons.

8. Method according to claim 1 in which R is a-monovalent saturated aliphatic hydrocarbon radical having the same number of carbon atoms as at least one of the unsaturated hydrocarbons.

9. Method according to .claim 1 in which saidunsaturated hydrocarbons contain admixed therewith materials substantially inert to said activators.

10. Method according to claim 9 in'which saidinert materials are substantially saturated aliphatic hydrocarbons.

11. Method for dimerizing a-olefins having at least 3 carbon atoms, which comprises heating such olefins at a temperature of about -220 C. in the presence of a dimerization activator having the general formula M(R)n, in which Me is a metal selected from the group consisting of beryllium, aluminum, gallium and indium, R is at least one substituent selected from the group consisting of hydrogen, monovalent saturated aliphatic hydrocarbon radicals and monovalent aromatic hydrocarbon radicals, and n is the valence of the metal Me, and recovering a dimer.

12. Method according to claim 11 in which said heating is eifected at increased pressure.

13. Method according to claim 11 in which said olefin is propylene and said recovered dimer is l-methyl-lpropyl-ethylene.

14. Method for dimerizing olefins having a double bond in the intermediate position which comprises heating such olefins at a temperature of about 120 to 250 C. in the presence of dimerization activator having the general formula M6(R)n, in which Me is one metal selected from the group consisting of beryllium, aluminum, gallium and indium, R is at least one substituent selected from the group consisting of hydrogen, mono valent saturated aliphatic hydrocarbon radicals and monovalent aromatic hydrocarbon radicals, and n is the valance of the metal Me, and recovermg a dimer.

References Cited in the file of this patent UNITED STATES PATENTS OTHER REFERENCES Taylor et al., Journal American Chemical Society, vol. 52, p. 1111-1121, March 1930. 

1. METHOD FOR DIMERIZING UNSATURATED STRAIGHT-CHAIN HYDROCARBONS CONTAINING MORE THAN TWO CARBON ATOMS IN THE MOLECULE, WHICH COMPRISES HEATING SUCH HYDROCARBONS AT A TEMPERATURE OF ABOUT 80 TO 250* C. IN THE PRESENCE OF A DIMERIZATION ACTIVATOR HAVING THE GENERAL FORMULA ME(R)N, IN WHICH ME IS ONE METAL SELECTED FROM THE GROUP CONSISTING OF BERYLLIUM, ALUMINUM, GALLIUM AND INDIUM; R IS AT LEAST ONE SUBSTITUENT SELECTED FROM THE GROUP CONSISTING OF HYDROGEN, MONOVALENT SATURATED ALIPHATIC HYDROCARBON RADICALS, AND MONOVALENT AROMATIC HYDROCARBON RADICALS, AND N IS THE VALENCE OF THE METAL ME, AND RECOVERING A DIMER. 